Blood pressure transducers are commonly used in hospitals to display or record a continuing indication of the patient's blood pressure. In typical applications, the transducer is taped to the patient's arm and connected to a vein through a cannula with a stopcock. A cable about one foot in length extends from the transducer to a connector which is also affixed to the patient's arm. In a preferred type of apparatus, the connector contains compensating circuitry for the calibration and temperature-tracking of the transducer, and provides for the universal interconnection of the transducer assembly to various types of monitors.
In a typical hospital environment, the blood pressure monitor is mounted on a shelf or other location at least several feet away from the patient and often not readily accessible by the nursing staff while attending the patient. One of the duties of the nurse is to check from time to time whether the transducer system is functioning, particularly after the patient has been moved or the transducer system has been manipulated.
A null check of the transducer can readily be accomplished by closing the stopcock and venting the transducer to atmosphere. A pressure check is ordinarily accomplished by pressing a test button on the monitor which shunts one of the arms of the transducer's strain gauge bridge with a known resistance such that, if the transducer circuitry is functioning properly, the monitor should show a steady predetermined pressure reading.
It has long been felt desirable to give the nursing staff the ability to make the pressure check while attending the patient and without going to the monitor. However, it has previously been considered impractical to do so because the patient was likely to accidentally depress the pressure check button and thereby to disable the monitoring equipment.